Electrical heating unit.



F. KUHN.

515011110111 HEATING UNIT.

. 191 I. 1,170,165. Patented Feb.1, 1916.

2 SSSSSSSSSSSSS 1.

F g JV J V F.-KUHN.

ELECTRICAL HEATING UNIT.

APPLICATION FILED MAR. 6, 1911.

1,170,165. Patented Feb. 1, 1916.

2 SHEETSSHEET 2.

UNITED STATES PATENT OFFICE.

FRANK KUHN, OF DETROIT, MICHIGAN, ASSIGNOR T0 AMERICAN ELECTRICAL HEATER COMPANY, 013 DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

ELECTRICAL HEATING UNIT.

Specification of Letters Patent.

Patented Feb. 1, 1916.

ing at Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Electrical Heating Units, of which the-following is a specification, reference being had therein to the accompanying drawings.

The invention relates to electrical heating units and is more particularly designed for use in connection with sad-irons, but is also applicable to other uses.

It is the object of the invention to obtain a construction of sheathed or armored resistance which may be detachably engaged with the body to be heated, and the invention consists in the construction and method of manufacture as hereinafter set forth.

In the drawings, Figure 1 is a plan view of the various elements composing the unit; Fig. 1 is a plan view of one of the core plates detached; Fig. 1 is a plan view of the upper insulating plate detached; Fig. 1 is a plan view of the lower metallic plate, dctached; Fig. 1 is a plan view of the upper metallic plate detached; Fig. 2 is a diagrammatic cross section showing the manner of assembling the elements; Fig. 3 is an enlarged cross section through the assembled unit; Fig. 4 is a longitudinal section through the terminal connection; and Fig. 5 is a perspective view of the unit complete.

In the construction of electrically-heated instruments, it is desirable to provide detachable heating units, and it is also desirable to construct these units so as to have as large a heat-conducting surface as possible in contact with the body to be heated. Furthermore, the rapidity with which the heat may be transferred from the element to the body depends largely upon the perfection of the mechanical joints or contact between the element and the body. I have therefore devised a construction in which the heating unit is inclosed in a metallic sheath adapted to lie adjacent to the surface of the body to be heated and having sufficient flexibility to accurately conform to the shape thereof.

In detail, A is a sheet metal blank of the desired form for the unit, that shown being the shape of a sad-iron. At the margin of this blank are flanges B and in the center a longitudinally extending aperture C is formed having flanges C.

D is a stay or uncut portion extending across the aperture C and having a round aperture E therein for engaging a securing pin.

F is the resistance element preferably in the form of a flat ribbon which is wound about a core G of insulating material preferably a sheet of mica. The edges of this core are notched at G to receive the convolutions of the resistance winding and to hold the samefrom displacement. The core G is preferably formed in two sections to be arranged upon the blank A on oppositesides of the central aperture C therein, but the resistance conductor is preferably continuous and bridges across the gap between the core sections at the forward end thereof.

H are insulating plates preferably of mica conforming to the shape of the blank A, one being arranged between said blank and the resistance element, and another being placed above the resistance element.

I are metallic plates overlying the upper insulating plate H but having a portion projecting beyond the edge of said insulating plate and in a position to contact with the end portion of the resistance winding. To compensate for the thickness of the insulating plate H this end portion I of the plate I is slightly off-set or bent downward ,so as to insure firm contact with the resistance winding.

I is an extension of the plate I which is bent upward to form an electrical terminal, and I is a contact post secured to this terminal.

With the parts as thus far described, to facilitate the manufacture and assembling, corresponding apertures J are formed in the blank A, core member G and plate I which apertures are adapted to receive the guide pins K on the assembly jig K. These pins will hold the parts from relative displacement and the apertures in the core member G are so located as to avoid the windings on said core. Each of the insulating plates H is also provided with apertures J, and thus the parts may be assembled and held in position as shown in Fig. 2. After the plates 1 are in place another insulating plate H is placed therebetween and then the upper metallic plate L of the sheathing is placed in position. The marginal flanges B are then turned down over the plate L and also the flanges C on opposite sides of the aperture C, with the result that all of the parts are clamped into firm contact with each other.

It will be observed by inspection of Fig. 3 that the core member G is smaller than the bottom and top plates of the sheath and that the insulating plates H extend beyond the margin of said core as well as that of the plate I. Thus when the flange B is turned down it will bend down with it the marginal projecting portions of the insulating plates pressing these to a position where they are a less distance apart than the thickness of the heating element and preferably 'into contact with each other,.effectually preventing any lateral shifting of the core member or the plate I. As these members have been accurately positioned in relation to each other by the pins K during assembly, it is obvious that after the flanges are turned down they will be permanently held in this'position which is such as to preyent danger of short circuiting the resistance conductor.

The terminal posts I are adapted to engage with corresponding socket contacts in the attachment plug but it has been found in practice that the slight arcing produced whenever the plug is attached or detached will eventually injure the surface of the posts. I therefore preferably construct these posts so as to be removable from the plate I permitting replacement as: often as necessary. As shown, the extension I of the member I is secured to the socket section I which is internally threaded to receive a threaded shank I of the contact post 1 Thus at any time when the posts become damaged they may be quickly removed and replaced by others.

What I claim as my invention is:

1. An electrical heating unit comprising superposed .sheet metal plates seamed together at the margin and centrally thereof, a resistance element extending on opposite sides of the central seam, separate terminal contact plates upon opposite sides of said seam, and insulating layers all arranged to form a series intermediate said superposed plates and clamped by the seaming thereof. v

. 2. A resistance element for'sad-irons comprising a sheathing corresponding in contour to the work body of the iron and having marginal seams and a central longitudinal seam, insulator core sections upon opposite sides of said central seam, a continuous resistance conductor wound upon said insulator core sections, separate terminal connecting plates corresponding substantially with the contour of said insulator core sections and arranged thereabove, terminals extending outward from said terminal connecting plates, and insulating layers, said layers, terminal connecting plates and resistance element being clamped by the marginal and central seams of said sheathing.

3. An electrical heating unit comprising an outer sheath, a conducting element and insulating layersarranged on opposite sides of said element and projecting beyond the edges thereof, the 'outer sheath being seamed to clamp the projecting edges of the insulating layers a less distance apart than the thickness of the element.

4. An electrical heating unit comprising a conducting element, insulating layers of greater width than the conducting element, and an outer sheath seamed at the margin to clamp said element and insulating layers with the-edges of the latter a less distance apart tha'n'the thickness of the element.

5. .An electrical heating unit, comprising an outer sheath, a conducting element and insulating layers arranged in series, the outer sheath and insulating layers being of greater width than the element, the central and marginal portions of said outer sheathing being seamed, said marginal portion clamping the projecting edges of the insulating layers a less distance apart than the thickness of the heating element. 4

6. In anelectrical heating unit, the combination with outer plates, of a resistance element, insulating plates on opposite sides of said resistance element, a terminal connecting plate provided with an embossed portion to compensate for the thickness of the insulating layer and being in positive contact with a portion of said resistance element, and an insulating plate on the op posite side of said terminal connecting plate,

and means for clamping said resistance element, insulating plates and terminal con necting plate between said outer plates.

7. an electrical heating unit, comprising a heating element, insulating layers of greater width than the heating element, po-

sitioned on opposite sides thereof, and means for clamping the projecting portions of said insulating layers together a substantial less distance apart than the thickness of said heating element to prevent lateral shifting thereof;

8. An electrical heating unit, comprising a resistance element, a terminal connecting plate having a portion in metallic contact distance apart approximately equal to the with said resistance element, the remaining thickness of the resistance element. 10 portion being insulated therefrom, insulat- In testimony whereof I a fiix my signaing layers of greater width than said resistture in presence of two witnesses.

ance element and said terminal connecting FRANK KUHN. plate, positioned on the outer sides thereof, Witnesses:

and means for clamping the projecting por- W. J. BELKNAP,

tions of said insulating layers together at a JAMES P. BARRY.

copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

. Washington, D. 0." 

